1. Field of the Invention
The present invention relates to a quantum wire structure and a method for producing the same, and more particularly, to a curved electron waveguide structure and a method for producing the same for confining an electron wave by a curve of a quantum well.
2. Description of the Prior Art
Desired characteristics such as increases in luminous efficiency, electron running speed, and electro-optical non-linear effect have been verified as quantum effects in a quantum well structure. Such a structure in which these effects can be expected is a quantum wire structure. In a quantum wire structure, the movement of electrons ordinarily restricted in a two-dimensional direction is further regulated in an additional dimensional direction due to the quantum well structure, thereby realizing a one-dimensional electron gas condition.
Up until now, various kinds of methods for realizing the quantum wire structure have been proposed. Examples of these include a method for growing crystals on an off-substrate using a characteristic that crystals are likely to grow in an atom layer step by Metal Organic Chemical Vapor Deposition (MOCVD) or a molecular beam epitaxial (MBE) method, and a method using an ion injection. However, highly desirable quantum wire effects cannot be achieved even when these methods are used.
As a result, the growth of a quantum well on a patterned substrate has been studied as a method having higher controllability (see Japanese Laid-open Patent Publication No. 2-237110). According to this method, a quantum well layer is grown on a substrate having unevenness in a stripe shape, whereby electrons are confined in a wire-shaped portion having a low potential formed in the unevenness. The advantages of this method are as follows:
(1) It is not necessarily required to develop processing technique on the order of 10 nm which is size of the quantum wire itself; and PA1 (2) since the quantum wire structure can be produced by one crystal Growth, it is possible that the contamination of crystal defects is minimized, etc.
However, according to this method, the crystal growth rate in the unevenness is different from that on the flat portion and is varied in accordance with the shape of the unevenness. As a result, it is almost impossible that a quantum wire is produced with satisfactory controllability, in-plane uniformity, and reproducibility as designed. In the same Way, when an optical waveguide is formed by utilizing a curve in growing crystals, reproducibility and controllability cannot be obtained.
As is described above, in the past, it has been difficult to produce a quantum wire structure with satisfactory controllability, reproducibility, and in-plane uniformity. Therefore, various improvements of characteristics which are logically expected in various devices have not yet been achieved.